To begin most of the many versions of the game of pool, it is necessary to arrange fifteen pool balls into a triangular formation with the ball at the apex of the triangle centered over a white spot on the green table and the five balls forming the base of the triangle lined up parallel to the end of the pool table.
A triangular rack with three similar upstanding walls is traditionally used to effect the foregoing arrangement of the pool balls. To permit convenient loading of the fifteen balls into the rack lying on the pool table, the conventional rack is sized so that the balls fit loosely within the rack. This means that the interior corners of the oversized rack which are smoothly curved will have a radius which somewhat exceeds the radius of the pool balls.
The usual way of arranging the fifteen pool balls within the oversized rack into a compact triangle with the foremost or apex ball of the triangle correctly positioned over the white spot and the five balls at the base of the triangle lying parallel to the end of the pool table has been to move the rack back and forth so that the apex ball rolls back and forth over the white spot. Then the person racking the balls uses his fingers or thumbs trying to push the row of five balls at the base of the triangle forward when the apex ball is stopped lying over the white spot.
However, due to sticky fingers or uneven pressure on the row of five balls or lack of attention by the ball racker or other reasons, the fifteen balls usually do not end up in the desired compact triangle with its apex right over the white spot. Moreover, since the curved interior apex of the rack cannot tightly grip the apex ball due to its larger radius of curvature, the apex ball tends to roll away from the two balls behind it as the rack is removed.
Thus various mechanical means have been employed or at least suggested to achieve the desired compact triangular arrangement of the balls. Elongated solid or tubular cylinders which fit within the rack behind the rearmost row of five balls have been suggested but such cylinders present a problem of removal without disrupting the compact grouping of the balls. Also suggested has been a movable elongated panel or bar which normally lies against the rear wall of the rack but which can be pushed forward during racking to force the balls into a compact triangle. See, for example, Smith U.S. Pat. No. 4,903,965 and the several earlier patents containing similar suggestions cited in Smith '965. But, so far as I am aware, the complicated mechanisms suggested in these patents have not been on sale or met with commercial success.